PubMed comprises more than 24 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.

PubMed - Lineage

PubMed comprises more than 24 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.

Works in the public domain are those whose intellectual property rights have expired, have been forfeited, or are inapplicable. Generally, stuff that is created by employees of the Federal Goverment of the US is automatically released as public domain.